Theme: a data layer; a theme contains spatial and tabular data for only one type of ecological or cultural feature. Themes' spatial and tabular data can be combined to form new themes or stacked to produce views.

Polygon: a feature used to represent a distinct area. A polygon is defined by the lines that make up its boundary and an identification label point inside its boundary. Polygons have attributes that describe the feature (lake, pitstructure, political state, etc.) they represent.

Line: a set of ordered co-ordinates that represent the shape of geographic features too narrow to be displayed as polygons with area at the given scale (contours, street center lines, or streams) or linear features with no area (county boundary lines). A line is synonymous with an arc.

Point: a zero-dimensional abstraction of an object represented by a single X,Y co-ordinate. A point normally represents a geographic feature too small to be displayed as a polygon with area; for example, the location of a small structure on a small-scale map or the location of an isolated artifact on a 7.5 minute topo map.

Introduction to and Goals of the GIS Teaching Module

The goal of this GIS teaching module is two-fold. First, the lab exercise will introduce the world of GIS-aided spatial analysis, a world inhabited by a rapidly growing population of anthropologists! You will answer research questions based on personal interpretations of spatial data, just as you would after collecting data in the field as a professional archaeologist. Your interaction between GIS maps and anthropological research questions is intended to strengthen your understanding of spatial analysis, settlement archaeology, and GIS as anthropological research tools.

The lab exercise should also prompt you to consider and discuss possible ways in which cultural and ecological factors influenced the locations of agave rockpile fields during the Early Classic Period Hohokam occupation of the Marana Community (A.D. 1150 - 1450). The ecological environment (temperature, moisture, potable water, food resources, soil type, availability of construction materials, etc.) clearly affected the locations of these fields. The cultural landscape that Hohokam farmers constructed within the ecological landscape also influenced site location. Therefore, prehistoric site locations were selected after consideration of the ecological AND cultural features that were present on the landscape (e.g., a farmer might have located a rockpile field on a lesser quality soil because the best soil was too close to a hostile village or because the plot was conveniently adjacent to a relative's field or house).

This exercise allows you to formulate your own explanation for site locations after considering all spatial information. Many of the GIS maps, to which you will be introduced in the tutorial segment, provide the visual data that you will need to formulate and support your answers to the following archaeological research questions.

General Module Directions and GIS Definitions

When prompted to display and on your screen, simply click on the specified link (all caps, blue, and underlined) within the text of the directions. The link leads to an image of the specified theme or view, all of which were created in ARC/INFO and ArcView and then converted into digital image files. Tables 1 and 2 below provide descriptions of each theme and view included within this module.

The spatial data layers you view on screen are called themes or views. Themes are data layers containing only one component of spatial information. For example, is a theme because it contains information for Zone 2 habitation sites only. A view, on the other hand, is a composite made of more than one theme. Views contain multiple components, or stacked data layers. Click on to see an example of a view that contains three separate polygon themes
(, , ).

Each theme contains only one of three types of data: , , or . Polygon themes possess irregularly shaped, shaded, enclosed areas that may represent any feature with area, such as archaeological sites, towns, countries, geologic deposits, etc. Linear archaeological surveys conducted in and around Tucson, Arizona, which you can view by clicking on , are examples of the type of data contained in a line theme. indicates the distribution of isolated Archaic Period projectile points in Pima County and serves as an example of a point theme. Polygons possess length, width, and area; lines possess length but not width or area; and points possess none of the three (theoretically). As a composite of many themes, a view may possess one or all three types of data.